SUMMARY : Harrison’s Principles of Internal Medicine has a long and distinguished tradition in the field of hematology. Maxwell Wintrobe, whose work actually established hematology as a distinct subspecialty of medicine, was a founding editor of the book and participated in the first seven editions, taking over for Tinsley Harrison as editor-in-chief on the sixth and seventh editions. Wintrobe, born in 1901, began his study of blood in earnest in 1927 as an assistant in medicine at Tulane University in New Orleans. He continued his studies at Johns Hopkins from 1930 to 1943 and moved to the University of Utah in 1943, where he remained until his death in 1986. He invented a variety of the measures that are routinely used to characterize red blood cell abnormalities, including the hematocrit, the red cell indices, and erythrocyte sedimentation rate, and defined the normal and abnormal values for these parameters, among many other important contributions in a 50-year career. The bringing together of hematology and oncology in a single text is unusual and we hope it is useful. Like many areas of medicine, the body of knowledge relevant to the practice of hematology and oncology is expanding rapidly. New discoveries with clinical impact are being made at an astounding rate; nearly constant effort is required to try to keep pace. It is our hope that this book is helpful to you in the struggle to master the daunting volume of new findings relevant to the care of your patients.